Wednesday, July 29, 2015

DNS Host A Record Being Deleted on Server Reboot

Our company Avantgarde Technologies was performing a domain controller upgrade for a client from Server 2008 R2 domain controllers to Server 2012 R2. After deploying the new domain controllers we went through the process of updating the DNS Client records on member servers which had these addresses statically assigned.

After updating a few DNS client settings on member servers, our customer complained that when they rebooted these servers, the member servers Host A record in DNS disappeared. This issue only occurred with 2008 and 2008 R2 member servers, 2012 servers were not affected.

After looking into this issue, we found that there is a bug with the DNS client in Server 2008 and Server 2008 R2. Windows Vista and Windows 7 clients are also effected. This bug is documented under KB2520155 and Microsoft has released a hotfix.

The issue is simple, as per the Microsoft KB article:

"This issue occurs because of an issue in the DNS Client service. When the DNS server configuration information is changed on a client, the DNS Client service deletes the DNS host record of the client from the old DNS server and then adds it to the new DNS server. Because the DNS record is present on the new server that is a part of the same domain, the record is not updated. However, the old DNS server replicates the deletion operation to the new DNS server and to other DNS servers. Therefore, the new DNS server deletes the record, and the record is deleted across the domain."

To get the member server to re-register itself in DNS, you must perform one of the following actions:

Restart the computer.

Restart the DNS Client service.

Run the ipconfig /registerdns command.

After the dynamic registration is re-created the record will not delete unless the DNS client addresses are again changed on the server.

If you require the ability to change the DNS client addresses on member servers on a regular basis, I strongly recommend installing the patch which is available from KB2520155. In this instance we did not install the patch as this customer does not change the DNS client addresses on member servers on a regular basis.

For this customer we did not install the patch, we simply performed an ipconfig /registerdns on any servers 2008 R2 servers after their DNS client was updated and server was rebooted.